Creatine kinase activity and isoenzyme pattern in various normal tissues and neoplasms.

I measured total creatine kinase (CK; EC 2.7.3.2) activity and isoenzyme pattern in normal and neoplastic tissues. CK activity was detected in all of them examined. In various tumors it was greater than, less than, or the same as that in normal tissue, no clear correlation being seen between total activity and growth rate or degree of differentiation. In several cases, there was a greater proportion of the CK-MM isoenzyme, and 15 of 53 cases showed an atypical CK-MM band. The atypical CK-MM band, also reported by others, might be an insensitive and nonspecific tumor marker. The CK-BB isoenzyme, ubiquitous in neoplastic tissues, might accordingly be a nonspecific marker. Total CK activity was very low in most tumor tissues. Presumably a bulky tumor or an advanced stage of malignancy is a requisite to release of routinely detectable CK-BB into the circulation.